SOLUTION: P(x)= ax^3- bx^2+cx-8 has zeros 2 and -1. P(3)= 28. Evaluate a, b and c. this is all I have so far, how do I solve this question? P(x)= (x-2)(x+1)Q(x) Thank you in advanced

Algebra ->  Equations -> SOLUTION: P(x)= ax^3- bx^2+cx-8 has zeros 2 and -1. P(3)= 28. Evaluate a, b and c. this is all I have so far, how do I solve this question? P(x)= (x-2)(x+1)Q(x) Thank you in advanced       Log On


   

Question 1098678: P(x)= ax^3- bx^2+cx-8 has zeros 2 and -1. P(3)= 28. Evaluate a, b and c.
this is all I have so far, how do I solve this question?
P(x)= (x-2)(x+1)Q(x)
Thank you in advanced :)
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
a%282%29%5E3-b%282%29%5E2%2Bc%282%29-8=0
8a-4b%2B2c-8=0
8a-4b%2B2c=8
4a-2b%2Bc=1

-

-a-b-c-8=0
a%2Bb%2Bc=-8
-
P%283%29=28
a%283%29%5E3-b%283%29%5E2%2Bc%283%29-8=28
27a-9b%2B3c-8=28
27a-9b%2B3c=36
9a-3b%2Bc=4


System to solve:
system%284a-2b%2Bc=1%2Ca%2Bb%2Bc=-8%2C9a-3b%2Bc=4%29